The pore structure of compacted and partly saturated MX-80 bentonite at different dry densities

Keller, Lukas; Seiphoori, Ali; Gasser, Philippe; Lucas, Falk; Holzer, Lorenz; Ferrari, Alessio

doi:10.1346/CCMN.2014.0620302

Publication type:	Article in scientific journal
Type of review:	Peer review (publication)
Title:	The pore structure of compacted and partly saturated MX-80 bentonite at different dry densities
Authors:	Keller, Lukas Seiphoori, Ali Gasser, Philippe Lucas, Falk Holzer, Lorenz Ferrari, Alessio
DOI:	10.1346/CCMN.2014.0620302
Published in:	Clays and Clay Minerals
Volume(Issue):	62
Issue:	3
Page(s):	174
Pages to:	187
Issue Date:	2014
Publisher / Ed. Institution:	Clay Minerals Society
ISSN:	0009-8604 1552-8367
Language:	English
Subjects:	Map
Subject (DDC):	620.11: Engineering materials
Abstract:	Compacted MX-80 bentonite is a potential backfill material in radioactive-waste repositories. Pore space in MX-80 has been the subject of considerable debate. 3D reconstructions of the pore space based on tomographic methods could provide new insights into the nature of the pore space of compacted bentonites. To date, few such reconstructions have been done because of problems with the preparation of bentonite samples for electron microscopy. The nanoscale intergranular pore space was investigated here by cryo-Focused Ion Beam nanotomography (FIB-nt) applied to previously high-pressure frozen MX-80 bentonite samples. This approach allowed a tomographic investigation of the in situ microstructure related to different dry densities (1.24, 1.46, and 1.67 g/cm3). The FIB-nt technique is able to resolve intergranular pores with radii >10 nm. With increasing dry density (1.24-1.67 g/cm3) the intergranular porosity (>10 nm) decreased from ∼5 vol.% to 0.1 vol.%. At dry densities of 1.24 and 1.46 g/cm3, intergranular pores were filled with clay aggregates, which formed a mesh-like structure, similar to the honeycomb structure observed in diagenetic smectite. Unlike 'typical' clay gels, the cores of the honeycomb structure were not filled with pure water, but instead were filled with a less dense material which presumably consists of very fine clay similar to a colloid. In the low-density sample this honeycomb-structured material partly filled the intergranular pore space but some open pores were also present. In the 1.46 g/cm3 sample, the material filled the intergranular pores almost completely. At the highest densities investigated (1.67 g/cm3), the honeycomb-structured material was not present, probably because of the lack of intergranular pores which suppressed the formation of the honeycomb framework or skeleton consisting of clay aggregates.
URI:	https://digitalcollection.zhaw.ch/handle/11475/2127
Fulltext version:	Published version
License (according to publishing contract):	Licence according to publishing contract
Departement:	School of Engineering
Organisational Unit:	Institute of Computational Physics (ICP)
Appears in collections:	Publikationen School of Engineering

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Keller, L., Seiphoori, A., Gasser, P., Lucas, F., Holzer, L., & Ferrari, A. (2014). The pore structure of compacted and partly saturated MX-80 bentonite at different dry densities. Clays and Clay Minerals, 62(3), 174–187. https://doi.org/10.1346/CCMN.2014.0620302

Keller, L. et al. (2014) ‘The pore structure of compacted and partly saturated MX-80 bentonite at different dry densities’, Clays and Clay Minerals, 62(3), pp. 174–187. Available at: https://doi.org/10.1346/CCMN.2014.0620302.

L. Keller, A. Seiphoori, P. Gasser, F. Lucas, L. Holzer, and A. Ferrari, “The pore structure of compacted and partly saturated MX-80 bentonite at different dry densities,” Clays and Clay Minerals, vol. 62, no. 3, pp. 174–187, 2014, doi: 10.1346/CCMN.2014.0620302.

KELLER, Lukas, Ali SEIPHOORI, Philippe GASSER, Falk LUCAS, Lorenz HOLZER und Alessio FERRARI, 2014. The pore structure of compacted and partly saturated MX-80 bentonite at different dry densities. Clays and Clay Minerals. 2014. Bd. 62, Nr. 3, S. 174–187. DOI 10.1346/CCMN.2014.0620302

Keller, Lukas, Ali Seiphoori, Philippe Gasser, Falk Lucas, Lorenz Holzer, and Alessio Ferrari. 2014. “The Pore Structure of Compacted and Partly Saturated MX-80 Bentonite at Different Dry Densities.” Clays and Clay Minerals 62 (3): 174–87. https://doi.org/10.1346/CCMN.2014.0620302.

Keller, Lukas, et al. “The Pore Structure of Compacted and Partly Saturated MX-80 Bentonite at Different Dry Densities.” Clays and Clay Minerals, vol. 62, no. 3, 2014, pp. 174–87, https://doi.org/10.1346/CCMN.2014.0620302.